I've identified three companies each worth north of $50B who should be fighting over ownership of Foursquare. Apple, Facebook and Google? Nope. Visa ($110B), Mastercard ($66B) and American Express ($75B).

Your credit card company has a tremendous amount of data on where you, and the world, shops. Not purchases at the SKU level - they largely don't know what you bought at West Elm or Cheesecake Factory - but they do know that you spend $350 at a furniture store and $75 at a casual food chain. Now extrapolate this over millions of customers. Using covisitation data they could recommend to me other establishments visited by folks with similar spending patterns. "Hunter, because you enjoy West Elm you might also like SF Modern Design located at 1000 State St." This would be especially helpful when traveling.

But none of these credit card companies are (a) skilled at building consumer facing applications, (b) upstream of purchase decisions and (c) have place level data for retail establishments. Oh but wait, Foursquare has all of those. By combining with Foursquare, the credit card companies could finally justify and preserve their transaction fees (in the face of competition from other payment options) but working to drive demand to the local retailers. Today they do this in very non-scalable ways such as one-off marketing programs such as AmEx Small Business week.

To take it a step further, this would also give a credit card company the ability power loyalty programs at the retailer level using Foursquare check-ins combined with verified purchases to close the discovery<>transaction loop.

Is that a Foursquare-powered credit card in your pocket or is your app just happy to see me?